The present invention relates to apparatus and methods for the separation of a first granular material from a second granular material having a specific gravity less than the first granular material, and more specifically to methods and apparatus for separating gold dust and nuggets from sand, gravel, and other material with which gold dust and nuggets are normally associated in nature, and most particularly to such methods that can be implemented by hand.
Prior art gold panning techniques call for the use of a rounded, shallow container, normally referred to as a gold pan. Gold pans are available in a variety of rounded shapes; however, most are circular in plan view and have a relatively flat bottom from which the rounded sidewalls are uniformly upwardly and outwardly flared. Gold is separated from gold-containing gravel and sand; for example, by placing the mixture into a pan and vibrating the mixture in the pan so that, theoretically, the gold, which is the heavier material present, settles to the bottom. The top, or lighter, materials are then washed from the pan by causing the water in the pan to pass over the material in the pan and allowing the water after it has passed over the material to flow over the lip or edge of the pan, carrying with it some of the lighter material. When necessary, the water is replenished and the procedure repeated until all of the gravel and sand is washed away, leaving only gold. This technique has been utilized for gross separations of materials as well as for separating gold dust from the fine, black sands of no value.
The drawback to the prior art methods is that, as the water travels across the circular, flat bottom of the pan and approaches material normally placed at the intersection of the flat bottom and the rounded sides, the rounded sides tend to cause the water to converge on itself, in essence, pinching the sand and gold together. As the pinching effect occurs, there is a tendency for the sand and gold to mix and for the sand to be removed to a greater depth on the sides of the sand and gravel mass than occurs in the middle of the mass. As more and more of the black sand is removed, one of ordinary skill will readily see that the uneven removal of black sand and the mixture of the sand and gold will eventually lead to removal and thus loss of gold from along the sides of the mass. This and other drawbacks thus limit the utility and efficacy of prior panning techniques for final separation of small amounts of black sand from small amounts of gold dust. Accordingly, other separation techniques have been resorted to, including amalgamation. However, these other techniques all have their drawbacks and to some extent lead to the loss of certain amounts of gold dust.
Another drawback to prior art panning techniques is that sand, gravel, and gold are usually mixed together often in aggregate sizes that vary from each other significantly. Conventional panning techniques utilized to separate large granular materials from small granular materials result in the loss of some gold because sand particles, although having a lesser specific gravity than gold particles, tend to move through a mixture under the influence of gravity at a greater velocity than grains of gold. However, when granular materials of substantially similar size are placed together in a pan, the gold will quickly settle to the bottom upon vibration of the materials in the presence of water.
It is therefore a broad object of the present invention to provide methods and apparatus that employ panning techniques, but that enable one to effectively, efficiently, and almost completely separate fine granular material such as black sand from gold dust using techniques that are akin to, but different from, prior art panning techniques. It is a further object of the present invention to provide apparatus for retrieving gold from a pan once it has been separated from other granular material. It is a further object of the present invention to provide apparatus that can be utilized for the classification of sands and accompanying gold dust and nuggets into its component sizes so that materials of like size can be processed separately from materials of smaller or larger size. It is a further object of the present invention to provide an integrated classifying and panning system that can be compactly shipped and stored and that can be easily used, even by those who are neophytes to the panning arts.